Denitration mixed acid

Fig. 67. Rate of denitration of nitroglycerine, nitroglycol and dinitrodiglycol with mixed acid containing 7.5-10.5% HNO3 and 0.5-1. % H2O (Oehman [43]).

The results obtained by de Bruin and Witte [28a] make it clear that denitration of nitrocellulose with mixed acid may not reach completion even after one year (e.g. denitration of nitrocellulose of 13.95% N with mixed acid containing 21.9% HNOj and 16.9% HzO which yields nitrocellulose of 12.4% N on nitration). 

Fabel and Fritsche [29] have carried out experiments designed to re-nitrate and denitrate nitrocellulose, as follows. Cellulose was at first nitrated by immersion for 1 hr in one of a series of mixed acids A, B, C, or D (see Table 76). In succession... 

The accessibility of the OH groups in cellulose is 96-99% when nitrated with mixed acids. The accessibility of 0N02 in cellulose trinitrate on denitration is only ca. 70%. The latter value is much lower than the former because of the much higher crystallinity of the trinitrate compared with that of the lower substituted cellulose nitrates. The difference may explain why the rate of nitration is higher than that of denitration. The inaccessible regions in the nitration are to be attributed to cellulose junction points and in the denitration of cellulose trinitrate to trinitrate junction points . 

The mixed acid used in the nitration of cellulose has a compn dependent upon the type of cellulose nitrated, the degree of nitration desired, and the season of the year. During warm weather, it is necessary that the HN03 content be si greater than during winter, because of a tendency toward denitration of the mixed acid during warm weather. Variations in mixed... 

Diethyleneglycol dinitrate, like nitroglycerine, is prepared by nitrating diethylene glycol with mixed acid in batches or continuously. The diglycol is produced by synthesis. Since the waste acid is unstable, special formulations of mixed acid must be employed, and the mixed acid must be denitrated at the end of the nitration stage. 

Ffe. 5.10 The denitration rate of several nitrate esters in a mixed acid... 

The chemical stability of diethylene glycol dinitrate is roughly equal to nitroglycerine. Its hydrolysis is very slow even under hot water. For example, only 0.003 % diethylene glycol dinitrate is hydrolyzed at 60 °C for 120 h. It will be decomposed by waste acids. The denitration rate of diethylene glycol dinitrate in flie mixed acid with 7.5-10.5 % HNO3 and 0.5-1.1 % H2O is shown in Fig. 5.10. 

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

After mixing the two solutions, the temperature is raised to 50-55°C and maintained thus for 40 min. The presence of crystals in the semi-liquid mixture results in a violet colour which gradually changes to grey and then to yellow. Nitration is judged to be complete when the colour turns pale-yellow. The contents of the nitrator are then cooled to 20°C and the product is filtered off on a vacuum filter. Spent acid (1290 parts) is drawn off, y of it returning to nitration and y going to denitration. 

Clement and Riviere [59] also reported that cellulose acetate or a mixed ester — a nitrate-acetate — can be obtained by reacting cellulose nitrate with acetic anhydride, acetic acid, and sulphuric acid. According to more recent contributions, e.g. Wolfrom, Bower and Maker [60], the reaction should be performed as follows Cellulose nitrate is dissolved in the cold in a little sulphuric add and acetic anhydride, the surplus of acetic anhydride is then hydrolysed also in the cold, and cellulose acetate is extracted with a suitable solvent, such as chloroform. Other methods of acetylating nitrocellulose consist in reduction, for instance with zinc and hydrogen chloride, which entails denitration of the ester, followed by acetylation with acetic anhydride. All these reactions are carried out in the same vessel. Further, it is possible to synthesize mixed esters, cellulose nitrate-acetates, by subjecting cellulose to the action of a mixture that includes nitric acid, acetic add and acetic anhydride in the presence of sulphuric acid (Kruger [61]). The use of a large amount of nitric acid favours the formation of nitrocellulose only. Mixed esters are formed... 

The admixture of water with the acid remaining in the guncotton is accompanied by the development of an appreciable quantity of heat. Water used for this purpose should therefore be cooled at least to 4-8°C in order to prevent the temperature rising above the permitted limit, which would otherwise cause decomposition. In spite of this precaution, on mixing with the acid retained by the nitrocotton, a partial denitration always takes place, so the highest nitrated guncotton cannot be obtained by the Thomson process. 

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